Signal averaged electrocardiographic (SAE) detection of late potentials (LP) is a non-invasive method for detection of patients with aubythmogenic ventricle. The purpose of this study was to determine the correlation between SAE and inducibility of sustained ventricular tachycardia invasively by programmed stimulation (PS) in 30 patients with hypertrophic cardiomyopathy. The results show that based on certain LP indices SAE had a sensitivity and specificity of 85% and 94% respectively for induced VT. We conclude that SAE is a useful non-invasive test which in addition to PS may help to identify HCM patients with electrically unstable ventricles who may be at risk of sudden cardiac death.